Plug supervision trunk circuit



May 17, 1966 e. P. TRIPP PLUG SUPERVISION TRUNK CIRCUIT 2 Sheets-Sheet 1 Filed March 14 1963 INVENTOR,

GORDON P. TRIPP ATTORNEY.

May 17, 1966 G. P. TRIPP PLUG SUPERVISION TRUNK CIRCUIT 2 Sheets-Sheet 2 Filed March 14, 1963 INVENTOR, GORDON P, TRIPP ATTORNEY.

plexity to permit ease of maintenance.

United States Patent 3,251,950 PLUG SUPERVISION TRUNK CIRCUIT Gordon P. Tripp, Monmouth County, N.J., assignor to the United States of America as represented by the Secretary of the Army Filed Mar. 14, 1963, Ser. No. 265,601 3 Claims. (Cl. 179-43) The invention described herein may be manufactured and used :by or for the Government for governmental purposes, without the payment of any royalty thereon.

The present invention relates to a plug supervision trunk circuit and more particularly to a trunk circuit for interconnecting one manual telephone switchboard to a distant switchboard.

Those concerned with the development of telephone switchboards have long recognized the need for reducing the size and weight of the trunk circuits to permit portability of such switchboards and to also reduce their com The present invention fulfills this need.

It is therefore an object of this invention to provide a plug supervision trunk circuit which will substantially reduce the weight, size and complexity of the switchboard in which it is used. Other objects and advantages of the invention will hereinafter become more fully apparent from the following description of the annexed drawings, which illustrate preferred embodiments, and wherein:

FIGURE 1 shows a circuit diagram of one form of the invention; and

FIGURE 2 shows a circuit diagram of another form of the invention.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in FIGURE 1, a trunk circuit for interconnecting two switchboards A and B. The circuitry associated with each switchboard is identical and only switchboard A will be described in detail.

Switchboard A compri'ses a cord circuit 11a having a tip contact 12a and a ring contact 13a. Tip contact 12a is connected to a winding 14a of a differential polar relay having a second winding 15a, a magnetic armature 16a and a contact 17a. A diode 18a is connected between contact 17a and winding 14a. Winding 15a is connected between armature 16a and the ring contact 13a.

The differential polar relay is conventional. Such a relay is disclosed in detail in US. Patent 2,747,045, issued May 22, 1956. The direction and the amount of current in the windings 14a and 15a will determine the movement of magnetic armature 16a. Since the armatures are magnetic they will be latched or biased to remain in the position to which they are moved and will stay there until positively moved by the correct flow of current in the relay windings. However, mechanically connected to armature 16a is a shutter of a signal (not shown) on the switchboard panel. When armature 16a breaks with contact 17a the shutter is moved and the signal is exposed. The shutter and armature 16a are restored by replacing the cord 11a in the switchboard cord seat (not shown). This could be done by simply having the cord 11a abut armature 16a when the former is placed in the cord seat. However, in actual practice, the cord 11a, when placed in the cord seat, mechanically closes a switch in an auxiliary circuit (not shown) which actuates the relay thereby causing armature 16a to make with contact 17a to restore the shutter.

Also provided on the switchboard A is a jack 21a having a sleeve 22a, a tip spring 23a and a ring spring 24a. An insulating spacer 25a mechanically couples a spring switch 26a to ring spring 24a. Spring switch 26a is connected directly to the negative terminal of battery 29a whose positive terminal is grounded. The main lines 27 and 28 are connected to the tip and ring springs 23a and 24a respectively.

A second differential relay, having windings 31a and 32a, a magnetic armature 33a, and contacts 34a, 35a and 36a, is provided. Magnetic armature 33a normally connects the negative terminal of battery 37a (all batterys shown at switchboard A are actually the same battery, the different numbers being used for simplicity) to one side of winding 31a while the other side of winding 31a is normally connected to the main line 27 through contact 41a and tip spring 23a. The grounded positive terminal of battery 37a is connected to one side of winding 32a while the other side of winding 32a is connected to contact 36a. Contact 35a is connected to contact 42a which is normally broken with ring spring 24a which in turn is normally grounded through contact 43a. Magnetic armature 33a is mechanically coupled to the shutter of a second signal (not shown). The shutter, which is normally closed, exposes the signal when armature 33a breaks with contact 34a.

A third ditferential polar relay having windings 51a and 52a, magnetic armatures 53a, 54a, 55a and 56a, and contact-s 57a, 58a, 59a, 60a, and 61a, is provided. Magnetic armature 53a is normally made with contact 57a and connects ground to a contact 63:: which is normally broken with tip spring 23a. Armature 54a is normally made with contact 58a and connects the main line 28, through a winding 71a of a fourth differential polar relay, to a normally broken contact 65a. Armature 55a, normally broken with contact 59a, is connected to one side of winding 510.. Contact 59a is connected to contact 64a, which is normally made with spring 26a, and to contact 60a, which is normally broken with armature 56a. Armature 56a is normally made with contact 61a, which is both grounded and connected to one side of winding 72a of the fourth diiferential polarrelay. A battery 66a connects winding 51a to winding 52a with the latter winding connected to the negative terminal and the former winding connected to the positive terminal and ground. The fourth difierential relay also comprises a magnetic armature 730, connected to winding 72a, and normally broken contacts 74a and 75a connected to armature 56a and winding 52a respectively.

The circuit at switchboard B is identical to the circuit at A, as stated earlier, with the reference characters in the drawing being the same for corresponding parts except for the substitution of the letter [J for a. It is noted also, that the tip side of switchboard A is connected directly to the tip side of switchboard B while the ring side of the switchboards A and B are connected directly to each other.

The trunk of FIGURE 2 is similar to that of FIGURE 1 with some modifications such as the elimination of one diiferential polar relay. Those elements in the device of FIGURE 2 which correspond to the elements shown in FIGURE 1, have the same reference numerals increased by a factor of 100. Only the difierences between these two circuits will be explained in the detailed description of FIGURE 2.

In the circuit of FIGURE 2, a differential relay having windings 181a and 182a, magnetic armatures 153a and 183a, and contacts 157a 184a, 185a, and 186a, is provided in place of the third and fourth relays in the device of FIGURE 2. The positive terminal of battery 166a is grounded and connected to winding 181a while the tively. Magnetic armature 183a is connected to spring 126a which in turn is normally connected through contact 164a, battery 129a to ground. Contact 165a is connected directly to contact 135a.

The operation of the device of FIGURE 1 will now be described. It can be seen that there is no current flow in the trunk circuit as it lays idle i.e. in the position shown in FIGURE 1. Batteries 66a, 66b, 2% and 2% are all part of incomplete circuits. Battery 37a is connected to line 27 through contact 34a, armature 33a, coil 31a and contact 41a. However, no current flows since battery 37b is also connected to the main line and bucks battery 37a.

It a subscriber at station A wishes to contact a subscriber at station E, the operato at A will ins rt the cord 112; corresponding to the particular subscriber, in the iack 2121. Tip contact 12a will ca-m tip spring 23a which will break with contact 41a and make with contact 63a. Ring contact 13a will cam ring spring 24a which will break with contact 4301 and make with contact 42a. Spring 26a will also be moved to break with contact 64a and make with contact 65a. When this operation is performed the operator at station B will be signaled since a circuit is completed which consists'of ground at A, armature 53a, contacts 57a and 63a, ti-p spring 23a, line 27, tip spring 23b, contact 41b, coil 31b, armature 33b, contact 3411, battery 37b, ground at B, contact 43b, line 28, armature 54a, contact 58a, coil 71a, contact 65a, spring 26a, battery 29a and ground at A. Since batteries 37b and 2961, which are aiding each other, are connected in series with windings 31b and 71a, armatures 33b and 73a will make with contacts 35b, sca nin 75a respectiveiy. The oving of armature 3% will move the Sill-1t terexpasi the signgi to the operaterat station E. The ffiaking 6f arrr'iattife 73d will contact 74a and 75a is necesto reiiiove all voltages at station A from the main lifis 27 and 28, and to also, prepare the circuit for the next operation. Of course, the main lines 27 and 28 should be clear from all voltages when they are used for transmitting the voice signal. Therefore, when armature 73a makes with contacts 74a and 75a, a circuit is completed from ground at A, through battery 66a, coil 52a, contact 75a, armature 73a, contact 74a, armature 56a, contact 61a and ground at A. It should be noted that coil 72a is short circuited at this time from ground at A, through coil 72a, armature 73a, contact 74a, armature 56a, contact 61a, and back to ground at A, Since winding, 52a is now drawing urrent, armature 53a breaks with contact 57a, removing ground from line 27, armature 54a breaks with contact 5841, removing winding 71a and battery 29a from line 28 arma ture 55a makes with contact 59a, re aring the circuit .for later restoral and armature 56a breaks with 61a and makes with Contact 60a, removing the short circuit from winding 72a. Winding 72a is now part of a circuit from ground at A, through winding 72a, armature 73a, contact 75a, winding coil 52a, battery 66a, and ground at A. At this time, armature 73a will break with contacts 74a and 75a since current is now flowing in winding 72a.

In order for windings 51a, 52a, 51b or 52b to operate and move their associated armatures, a battery must be in series with the winding and no other windings can be in that circuit to limit the amount of current flow.

The circuit is now prepared for the next operation. One of the following two operations may now take place; (1) the operator at station A may abandon the call before the operator at B answers or (2) the operator at B may answer the signal,

The first operation is initiated by the operator at station A removing the cord 11a from the jack 21a. This operation will restore the circuit to the condition shown in FIGURE 1. 7

When cord 11a is removed from jack 21a, tip spring 23a, ring spring 24a and spring 26a return to the position shown in FIGURE 1. This completes a circuit from P will happen since the tip spring 23b ground at A, through battery 37a, contact 34a, armature 33a, Winding 31a, contact 41a, tip spring 23a, line 27, tip spring 23b, contact 4119, winding 31b, armature 3315, contact 36b, winding 32b and ground at B. Since windings 31b and 32b are in series aiding, armature 3312 will be moved before the armature 33a is given a chance to move. The shutter at B therefore, will be restored to conceal the signal and the armature 33a will not move at all since the circuit is altered to the condition shown in FIGURE 1 i.c. with batteries 37a and 37b bucking each other. Also, since spring 26a is now made with contact 640, battery 29a is connected across Winding 51a through contact 5% and armature 55a. When this occurs armatures, 53a, 54a, 55a and 56a are all returned to the position shown in FIGURE 1. The circuit is now restored to its initial position ready for another call.

If the operator at station B should answer the call of the o erator at station A, the cord 11b is inserted in the jack 21b. When this is done the signal at B is then canceled by-restoring the shutter and all voltages at station B are removed from lines27 and 28 except, of course, for any speech signal on cord 11b. Tip spring 23b will make with contact 63b, ring spring 2% will make with contact 42b and spring 26b will make with contact 6515. A circuit is now completed from ground at B, through winding 32b, contact 3612, armature 33b, contacts 35b and 4212, line 28, armature 54b, contact 58b, winding 71b, contact 65b, spring 26b, battery 2% and ground at B. The current flowing through winding 3213 will cause armature 33b to make with contact 34b, thereby moving the shutter to conceal the signal at station B. Armature 73b is also moved, and makes with contacts 7% and b. The closing of this switch has the same results as described earlier for the making of armature 73a with contacts 74a and 75a i.e. afmatures 53b, 54b and 56b break with contacts 57b, 58b and 61b respectively while armature 55b makes with con tact 5% thereby clearing lines 27 and 28 of all voltages and preparing the circuit for the next operation. Armature 73b finally breaks with contact 7412 and 75b.

The trunk circuit is now in condition for both operators 7 to speak to each other and to connect the subscriber at A to the called party at B.

The next possible operation will consist of either the operator at A or the operator at B removing the cord from its jack after either party has hung up. Assuming that the subscriber at A has hung up first, the operator at A would remove cord 11a from jack 21a. This operation will complete a circuit from ground at A, through battery 37a, contact 34a, armature 33a, winding 31a, contact 41a, tip spring'23a, line 27, t-ip spring 2312, up contact 12b, winding 14b, diode 1812', contact 17b, armature 16b, winding-15b, ring contact 13b, ring spring 24b, line 28, ring spring 24a, contact 43a and ground at A. This circuit consists mainly of one battery (37a) and three windings (31a, 14b and 15b). Since both windings 14b and 15b are in series aiding, armature 16b will operate and break with contact 17b to open the circuit before armature 33a has acbance to draw enough current to operate. The moving of armature 16b, of course, also moves the mechanically linked shutter to expose the signal to inform the operator at B that the call is completed. When the operator at B removes the cord 11b from jack 21b a oircuit is completed from ground at B through battery 2%, spring'26b, contacts 64b and 59b, armature 55b, winding 51b and ground at B. The current flow in winding 51b will restore armatures 53b, 54b, 55b and 56b to their initial position as shown in FIGURE 1. As was explained earlier armature 16b makes with contact 17b and its associated signal is concealed by the shutter, when .the cord 11b is replaced in the switchboard cord seat.

If the operator at A, who disconnected first, should reseize the trunk circuit by repluggin-g the cord 11a into the jack 21a before the operator at B disconnects, nothing is not made with contact 41b. However, when the operator at B has disconnected'and the cord 11a remains plugged in the jack 21a the conditions are then set for the signal at B to operate as before.

The circuit of FIGURE 2 operates substantially the same as the device of FIGURE 1. However, one relay is omitted from each switchboard. When the operator at A plugs cord 111a into jack 121a a circuit is completed from ground at A, through armature 153a, contact 157a, contact 163a, line 127, contact 141b, winding 131b, armature 133b, contact 134b, battery 137b, ground at B, contact 1431:, line 128, contacts 142a, 185a and 186a, winding 182a, battery 166a and ground at A. It can therefore be seen, that the signal at B will be exposed when armature 133b breaks with contact 13 4b. Also, at the same time armature 183a and 153a will be actuated to clear the lines 127 and 128 from any voltages at A. If the resistance of the ground between A and B is large the relay which operates the signal at B (and A) and the relay which clears the line at A (and B) must be so matched that they will operate simultaneously. However, if the ground resistance approaches zero the two relays will operate independently and their relative power ratings can vary widely.

If the operator at A should abandon the call before the operator at B answers, the shutter will return to the initial position, concealing the signal at B. When the operator at A removes the cord 111a from the jack 121a a circuit is completed from ground at A, through battery 137a, contact 134a, armature 133a, winding 131a, contact 141a, tip spring 123a, line 127, tip spring 123b, contact 141b, winding 131b, armature 133b, contact 136b, winding 132b, ground at B, contact 143b, r-in-g spring 124b, line 128, ring spring 124a, contact 143a and ground at A. In this circuit windings 131b and 13% are in series aiding to operate the armature 13%. Because of this armature 133b will be actuated to break the circuit before the Winding 131a has sutficient current to operate armature 133a. Thus the signal at B is concealed and the circuit returned to the initial condition.

However, when the operator at B answers this call by inserting the cord 111b in jack 121b a circuit is closed from ground at B through winding 132b, contact 136b, armature 133b, contact 135b contact 165b, spring 126b, armature 183b, contact 186b, winding 182b, battery 166k and ground at B. The winding 13% will restore the signal by operating armature 13% while winding 182b will operate armatures 153b and 18317, to clear the-lines 128 and 127 from any voltages.

Of course, either operator may disconnect when the call is completed. Assuming that the operator at A disconnects first the operator at B will then be signaled, since a circuit is completed from, ground at A through battery 137a, contact 134a, armature 133a, winding 131a, contact 141a, tip spring 123a, line 127, tip spring 123b, tip contact 112b, winding 114b, diode 118b, contact 1171;, armature 116b, winding 115b, ring contact 113b, ring spring 124b, line 128, ring spring 124a, contact 143a, and ground at A. Since windings 114b and 115k are in series aiding armature 1161: will break with contact 1171: before the signal associated with armature 133a Will operate. Therefore when armature 116b breaks with contact 117b the associated shutter will be moved and the signal at B will be exposed to inform the operator at B to disconnect the cord 111b, from the jack 1211). Of course, when the operator at B removes the cord 111b, from jack 12111 and replaces the cord in the cord seat, the circuit will return to the condition shown in FIGURE 2 for the same reasons given for the operation of the device of FIGURE 1. Also, if the operator at A should reseize the trunk by replugging the cord 111a, into the jack 121a before the operator at B disconnects, nothing will happen as was explained for the circuit of FIGURE 1. 7

It can therefore be seen, that a relatively simple and inexpensive trunk circuit has been provided wherein the only operation required by the operator is the insertion of the cord into the jack for seizing and the removing of the cord when disconnecting.

Obviously many modifications and variations of the present invention are' possible in the light of the above teachings. It is therefore to be understood, that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

l. A communication system comprising at least two manual switchboards and a trunk circuit, each said switchboard comprising a jack having a ring spring and a tip spring and a cord circuit for connection to said jack, said trunk circuit comprising first and second main-line conductors for connecting said tip springs to each other and said ring springs to each other respectively; signal means located at each of said switchboards, relay means connected to said trunk circuit for operating said signal means at one of said switchboards upon insertion of said cord circuit in said jack at the other of said switchboards and for restoring said signal means either upon the insertion of said cord circuit in said jack at said one of said switchboards or upon the removal of said cord circuit from said jack at the other of said switchboards, clearing rneans for clearing said main-line conductors of all signaling voltages upon the insertion of said cord circuits in said jacks and for restoring said circuit upon the removal of said cord circuits from said jacks.

2. A communication system comprising at least two manual switchboards and a trunk circuit, each said switchboard comprising a jack having a ring spring and a tip spring and a cord circuit for connection to said jack, said trunk circuit comprising first and second main-line conductors for connecting said tip springs to each other and said ring springs to each other respectively, signal means connected to said trunk circuit for signaling the operator at the distant switchboard upon insertion of the local cord circuit in the local jack and restoring either, upon the insertion of the distant cord in the distant jack, or upon the removal of said local cord from said local jack, and clearing means including two polar-ditferential-latched relays for clearing said main-line conductors of all voltage upon the insertion of said local cord circuit and said distant cord circuit in said local jack and said distant jack respectively and for restoring said circuit upon the removal of said cord circuits from said jacks.

3. A communication system comprising at least two manual switchboards and a trunk circuit, each said switchboard comprising a jack having a ring spring and a tip spring and a cord circuit for connection to said jack, said trunk circuit comprising first and second main-line conductors for connecting said tip springs to each other and said ring springs to each other respectively, signal means connected to said trunk circuit for signaling the operator at the distant switchboard upon insertion of the local cord circuit in the local jack and restoring either, upon the insertion of the distant cord in the distant jack, or upon the removal of said local cord from said local jack, and clearing means including a single polar-differential-latched relay for clearing said main-line conductors of all voltage upon the insertion of said local cord circuit and said distant cord circuit in said local jack and said distant jack respectively and for restoring said circuit upon the removal of said cord circuits from said jacks.

References Cited by the Examiner UNITED STATES PATENTS 3/ 1946 MacPherson 17943 

1. A COMMUNICATION SYSTEM COMPRISING AT LEAST TWO MANUAL SWITCHBOARDS AND A TRUNK CIRCUIT, EACH SAID SWITCHBOARD COMPRISING A JACK HAVINGL A RING SPRING AND A TIP SPRING AND A CORD CIRCUIT FOR CONNECTION TO SAID JACK, SAID TRUNK CIRCUIT COMPRISING FIRST AND SECOND MAIN-LINE CONDUCTORS FOR CONNECTING SAID TIP SPRINGS TO EACH OTHER AND SAID RING SPRINGS TO EACH OTHER RESPECTIVELY; SIGNAL MEANS LOCATED AT EACH OF SAID SWITCHBOARDS, RELAY MEANS CONNECTED TO SAID TRUNK CIRCUIT FOR OPERATING SAID SIGNAL MEANS AT ONE OF SAID SWITCHBOARDS UPON INSERTION OF SAID CORD CIRCUIT IN SAID JACK AT THE OTHER OF SAID SWITCHBOARD AND FOR RESTORING SAID SIGNAL MEANS EITHER UPON THE INSERTION OF SAID CORD CIRCUIT IN SAID JACK AT SAID ONE OF SAID SWITCHBOARDS OR UPON THE REMOVAL OF SAID CORD CIRCUIT FROM SAID JACK AT THE OTHER OF SAID SWITCHBOARDS, CLEARING MEANS FOR CLEARING SAID MAIN-LINE CONDUCTORS OF ALL SIGNALING VOLTAGES UPON THE INSERTION OF SAID CIRCUITS IN SAID JACKS AND FOR RESTORING SAID CIRCUITS IN SAID SAID CORD CIRCUITS FROM SIAD JACKS. 